There has been a long and steady demand for resins which may be cured to form polymeric resins which are difficultly inflammable or are both difficultly inflammable and resistant to high temperature.
In order to satisfy said demand, such cured resins should meet the classifications V0 or V1 according to "UL Specification 94 (Vertical Test)" (cf. Ju rgen Troitsch, "Brandverhalten von Kunststoffen" (1982 Munich/Vienna ISBN 3-446-13391-7), pages 396 to 399). As is generally known, the UL 94 Vertical Test is much severer than the UL 94 Horizontal Test. Thus, a resin classified in UL 94 HB does not meet classification UL 94 V0 or V1 (cf. Table 3 - Sample B).
Moreover, it is essential that the mechanical and electrical properties are not deteriorated by any additives, such as flame retardant additives. Furthermore, the halogen content, if any, of such resins should be as low as possible, since on combustion poisonous and corrosive smoke is developed. (cf. Jurgen Troitsch, "Flame Retardant Polymers Current Status and Future Trends", 4th Meeting of Fire Retardant Polymers, Freiburg i. Br. (Germany), 9 to 11 Sep. 1992).
From the publication U.S. Pat. No. 5,021,484 (Schreiber et al.) a resin is known which may be cured to form a polymeric resin which is difficultly inflammable and resistant to high temperatures, said resin being a mixture of:
(a) a resin component comprising at least one thermically PA1 (b) a second component comprising at least one flame retardant selected form the group consisting of: aluminium hydroxide; hydrated calcium magnesium. carbonate; magnesium hydroxide; elemental red phosphorus; oxygen acids of phosphorous; in-organic salts of oxygen acids of phosphorous; organic salts of oxygen acids of phosphorous;.v polyphosphates; boric acid; and salts of boric acid; PA1 (a) a component consisting of at least one thermically curable compound containing at least one 1-oxa-3-aza tetraline group; PA1 (b) a component consisting of at least one curable brominated epoxy resin; optionally PA1 (c) a component consisting of at least one curable non-brominated epoxy resin; and/or optionally PA1 (d) a curing agent for epoxy resins. PA1 Monovalent phenols, such as phenol, m- and p-cresol, m- and p-ethyl phenol, m- and p-isopropyl phenol, m- and p-isopropyloxy phenol, m- and p-chloro phenol, and beta-naphthol. Para- and meta-substituted phenols are preferred, since they do not include any blocked reactive positions. Also preferred are the phenols which are not alkyl substituted and not alkyloxy substituted, respectively. PA1 Bivalent phenols, such as 4,4'-dihydroxydiphenyl methane, 3,3'-dihydroxydiphenyl methane, 2,2'-bis-(4-hydroxyphenyl) propane, 4,4'-dihydroxy stilbene, hydroquinone, and resorcin. PA1 Low-condensed phenolic formaldehyde novolak resins, eventually mixed with a phenol. PA1 Aniline, phenylene diamine, benzidine, diaminodiphenyl methane, 2,2'-bis-(aminophenyl) propane, cyclohexylamine, ethylenediamine and propylenediamine, in particular p-phenylenediamine and 4,4'-diaminodiphenyl methane, aromatic amines being preferred. PA1 one or several glycidyl ethers of brominated phenols, in particular polyvalent phenols; PA1 one or several glycidyl ethers of condensation products of brominated phenols with aldehydes or ketones; or PA1 one or several glycidyl ethers of brominated novolaks. PA1 They have glass transition temperatures which are too low. PA1 In the case of combustion, they produce considerable quantities of the highly toxic carbonyldibromide, due to their high bromine content. PA1 Sidney H. Goodman, Handbook of Thermoset Plastics, Noyes Publications, Park Ridge, NJ; PA1 W. G. Potter, Epoxide Resins, Ilife Books, London; PA1 Henry Lee and Kris Neville, Handbook of Epoxy Resins, McGraw-Hill Book Company, New York/San Francisco/Toronto/London. PA1 4 hours at 180.degree. C.; or PA1 2 hours at 200.degree. C. PA1 24 hours at 220.degree. C. PA1 reinforcement fibers, such as glass, quartz, carbon, mineral and synthetic fibers, in the usual forms of short fibers, staple fibers, threads, fabrics or mats; PA1 plasticizers, especially phosphorous compounds; PA1 carbon black or graphite; PA1 fillers; PA1 dyestuffs; PA1 micro hollow spheres; PA1 metal powder: PA1 catalysts; and PA1 flame retardants, in particular the following groups of compounds, and compounds, respectively: PA1 as electric insulating materials, in particular for printed circuit boards; PA1 for supporting structures, in particular in aircraft constructions; PA1 wherever resins which are flame-resistant or resistant to high temperatures are to be used; PA1 as adhesives.
curable 1-oxa-3-aza tetraline groups containing compound; and of
and optionally also contains at least one curable epoxy compound.
It is true that by curing said known resin, products which are difficultly inflammable (meeting classification V0 or V1 in the UL 94 Vertical Test) and resistant to high temperatures may be obtained. However, their properties are still not sufficient for many uses, since the mechanical and electrical properties are deteriorated by the flame retardant additive (b).
Furthermore, the publication U.S. Pat. No. 3,058,946 (Naemitz) discloses a plastic product comprising a cured mixture of a brominated polyepoxide and a non-halogenated epoxide. However, this plastic product does not meet tho above-mentioned requirements, inasmuch as it does not reach classification V0 or V1 in the UL 94 Vertical Test, as evidenced by the comparative tests de-scribed hereafter (cf. Table 3).
Furthermore, the publication U.S. Pat. No. 4,727,119 (Berman et al) discloses selected halogenated, including brominated, epoxy resins wherein the halogen atoms are in the meta position with respect to a glycidyl ether group attached-to an aromatic ring. Whereas some of these epoxy resins show a remarkable inflammation resistance, they nevertheless are unsuitable for most purposes, since they have a filler content of up to more than 233 phr (parts per hundred parts of resin). For this reason they are in particular unsuitable for preparing printed circuit boards or high strength composites.